Used to use panasonic AA's from a dollar store- they barely last a day
Used in a Halo B with a hyperdash 2 motor
No safety device to prevent overcharging
A few days before the pack arrived, I had put a hyperdash 2 motor (RC cars motor) in in place of the stock one. Regular AA's couldn't even get it to spin, for some reason the halo thought there were low on charge even thogh they were brand new. I tried the BOne pack a few days later and it was amazing. It is sooo fast. The pack also hold it's charge for a very long time and saves weigh (though you won't notice). The best thing and real reason I got it was because it's rechargable, so in a few months it pays for itself. Dueydog is also very easy to work with and responds quickly.
The only disadvantage is that there is nothing to prevent it from overcharging and damaging your pack. It doesn't really matter though, the instructions say how long to charge it so I just write myself a bnuch of notes saying when to unplug it and haven't forgotten yet.
Defintely the best upgrade for your halo. Everyone should have one along with a delrin cone drive. IT WILL PAY FOR ITSELF